Old Style and New Style dates

On this marriage certificate, made out in 1907 in Warsaw (then part of the Russian Empire), the month is given as "November/December", and the day as "23/6". The Julian date 23 November corresponded to the Gregorian 6 December.

Excerpt of the cover page of a print of the Treaty of Lübeck (1629), with the Gregorian day (22) directly above the Julian (12), both before the name of the month, May. The treaty was concluded between Roman Catholic parties, who had adopted the Gregorian calendar, and Protestant parties, who had not.

Old Style (O.S.) and New Style (N.S.) are sometimes used with dates to indicate either whether the start of the Julian year has been adjusted to start on 1 January (N.S.) even though documents written at the time use a different start of year (O.S.), or whether a date conforms to the Julian calendar (O.S.), formerly in use in many countries, rather than the Gregorian (N.S.).[1][2][3][4] Closely related is double dating, which uses two consecutive years because of differences in the starting date of the year, or includes both the Julian and Gregorian dates.

The Gregorian calendar replaced the Julian in Catholic countries beginning in 1582. This change was also implemented in Protestant and Orthodox countries some time later. In England and Wales, Ireland, and the British colonies, the change of the start of the year and the changeover from the Julian calendar occurred in 1752 under the Calendar (New Style) Act 1750. In Scotland, the legal start of the year had already been moved to 1 January (in 1600), but Scotland otherwise continued to use the Julian Calendar until 1752.[5] Many cultures and countries now using the Gregorian calendar have different old styles of dating, depending on the type of calendar they used before the change.

The Latin equivalents of O.S. and N.S., which are used in many languages, are stili veteris (genitive) or stilo vetere (ablative), abbreviated st.v. and respectively meaning "(of) old style" and "(in) old style", and correspondingly stili novi or stilo novo, abbreviated st.n. and meaning "(of/in) new style".[6] The Latin abbreviations may be capitalized differently by different users, e.g., St.n. or St.N. for stili novi.[6] There are equivalents for these terms in other languages as well, such as the German a.St. ("alten Stils" for O.S.).

Start of the year in the historical records of Britain and its colonies and possessions[edit]

When recording British history it is usual to use the dates recorded at the time of the event, with the year adjusted to start on 1 January. But the start of the Julian year was not always 1 January, and was altered at different times in different countries.

From the 12th century to 1752, the civil or legal year in England began on 25 March (Lady Day)[7] so for example the execution of Charles I was recorded at the time in Parliament as happening on 30 January 1648 (Old Style).[8] In modern English-language texts this date is usually shown as "30 January 1649" (New Style).[1] The corresponding date in the Gregorian calendar is 9 February 1649, the date by which his contemporaries in some parts of continental Europe would have recorded his execution. In the 19th century, there was a difference of 12 days between the two calendars, so 25 March in the Julian calendar was 6 April in the Gregorian calendar, and 6 April is still the first day of the fiscal year in the United Kingdom.

The O.S./N.S. designation is particularly relevant for dates which fall between the start of the modern year (1 January) and the start of the contemporary year, which was 25 March in England and Wales until 1752 (see Julian year article).

During the years of transition between the first introduction of the Gregorian calendar in continental Europe and its introduction in Britain, contemporary usage in England started to change.[4] In Britain 1 January was celebrated as the New Year festival,[9] but the "year starting 25th March was called the Civil or Legal Year, although the phrase Old Style was more commonly used."[4] To reduce misunderstandings about the date, it was normal in parish registers to place a new year heading after 24 March (for example "1661") and another heading at the end of the following December, "1661/62", to indicate that in the following few weeks the year was 1661 Old Style but 1662 New Style.[10]

The Julian calendar was formerly in use in many European countries and their colonies, rather than the Gregorian calendar, which is currently in use in most countries. Consequently and to avoid ambiguity, "Old Style" (O.S.) and "New Style" (N.S.) are sometimes added to historical dates to identify which system is being used (when giving a date in the period when both systems were in parallel use). This notation is used in Western European (and colonial) history: similar notations are in use for the equivalent conversions in Eastern Europe and Asia.

For a period of 170 years (1582–1752) both dating systems were in concurrent use in different parts of Western Europe and its colonies. During this period, the Julian calendar had drifted by 10 days (16th and 17th centuries) and 11 days (18th century) from the Gregorian calendar (due to its excess of leap years), so dates differ between the systems. The switch to the Gregorian calendar for secular use occurred in Eastern Orthodox countries as late as the 20th century, and some religious groups in some of these countries still use the Julian calendar for ecclesiastical purposes.

Catholic countries such as Italy, Poland, Spain, and Portugal were first to change to the Gregorian calendar. Thursday, 4 October 1582 was followed by Friday, 15 October 1582, with ten days "missing". Countries that did not change until the 18th century had by then observed an additional leap year, necessitating eleven "missing days". Some countries did not change until the 19th or 20th century, necessitating one or two more "missing days".

France changed from Julian to Gregorian Calendar on 9 December 1582 (O.S.) so the next day was 20 December 1582 (N.S.). France used the French Republican Calendar from 22 September 1792 (N.S.) to 31 December 1805 (N.S.).

Ireland (under the provisions of the Calendar (New Style) Act 1750), Great Britain, and the British colonies changed from Julian to Gregorian Calendar at midnight on Wednesday 2 September 1752; the next day was Thursday 14 September 1752.[12]

The Ottoman Empire changed a year later, with 15 February (O.S. and last day of the old year) followed by 1 March 1917 (N.S. and first day of the new year). The beginning of the year was reset to 1 January starting in 1918. Year numbering, however, remained uniquely Turkish until 1926.[14]

In Russia, the terms "Old Style" and "New Style" have the same significance as elsewhere. The start of the year was moved to 1 January in 1700, but the Gregorian calendar was introduced there much later, on 14 February 1918 (Gregorian calendar) in Soviet Russia (which became the Soviet Union in 1922). Hence the October Revolution of 1917 is so called, despite having started on 7 November under the Gregorian calendar (25 October [Julian calendar]). Articles about the October Revolution which mention this date difference tend to do a full conversion to the dates from Julian to the Gregorian calendar. For example, in the article "The October (November) Revolution" the Encyclopædia Britannica uses the format of "25 October (7 November, New Style)" to describe the date of the start of the revolution.[15]

It is sometimes remarked that William Shakespeare and Miguel de Cervantes died on the same date, 23 April 1616, but not on the same day.[16] England was still using the Julian calendar in 1616, while Spain was using the Gregorian calendar. Cervantes actually died ten days before Shakespeare.

Issue 9198 of the London Gazette, covering Great Britain's switch from O.S. to N.S.

Occasionally using different calendars has caused confusion between contemporaries. For example, it is related[17] that one of the contributory factors for Napoleon's victory at the Battle of Austerlitz was the confusion between the Russians, who were using the Julian calendar, and the Austrians, who were using the Gregorian calendar, over the date that their forces should combine.[18] However, this tale is not supported in a contemporary account from a major-general of the Austrian Imperial and Royal Army, who tells of a joint advance of the Russian and Austrian forces (in which he himself took part) five days before the battle,[19] and it is explicitly rejected in Goetz's 2005 book-length study of the battle.[20]

Usually, the mapping of new dates onto old dates with a start of year adjustment works well with little confusion for events which happened before the introduction of the Gregorian calendar. For example the Battle of Agincourt is universally known to have been fought on 25 October 1415, which is Saint Crispin's Day. But for the period between the first introduction of the Gregorian calendar on 15 October 1582 and its introduction in Britain on 14 September 1752, there can be considerable confusion between events in continental western Europe and in British domains. Events in continental western Europe are usually reported in English language histories as happening under the Gregorian calendar. For example the Battle of Blenheim is always given as 13 August 1704. However confusion occurs when an event involves both. For example William III of England arrived at Brixham in England on 5 November (Julian calendar), after setting sail from the Netherlands on 11 November (Gregorian calendar), in 1688. For this reason, letters concerning diplomacy and international trade sometimes bore both old and new style dates to prevent confusion.

The Battle of the Boyne in Ireland took place a few months later on 1 July 1690 "Old Style". However, it is commemorated as "The Twelfth" on 12 July "New Style" by a public holiday in Northern Ireland, with the Orange parades, and is an exception to the usual historical method of commemorating events of that period within Great Britain and Ireland by mapping the Julian date directly onto the modern Gregorian calendar (as happens for example with Guy Fawkes Night on 5 November).

Because of the differences, English people and their correspondents often employed two dates, dual dating, more or less automatically. In his biography of Dr John Dee, The Queen's Conjurer, Benjamin Woolley surmises that because Dee fought unsuccessfully for England to embrace the 1583/84 date set for the change, "England remained outside the Gregorian system for a further 170 years, communications during that period customarily carrying two dates, one 'O.S.' or Old Style, the other 'N.S.' or New Style."[21] In contrast, Thomas Jefferson, who lived during the time that the British Isles and colonies eventually converted to the Gregorian calendar, instructed that his tombstone bear his date of birth in the Old Style and his date of death in the New Style.[22] At Jefferson's birth the difference was eleven days between the Julian and Gregorian calendars; thus his birthday of 2 April in the Old Style is 13 April in the New Style. Similarly, George Washington is nowadays officially reported as having been born on 22 February 1732, rather than on 11 February 1731/32 O.S.[23]

Japan, Korea, and China started using the Gregorian calendar on 1 January 1873, 1896, and 1912, respectively.[24][25] They had used lunisolar calendars previously. None of them used the Julian calendar; the Old Style and New Style dates in these countries usually mean the older lunisolar dates and the newer Gregorian calendar dates respectively. In these countries, the old style calendars were similar but not all the same. The Arabic numerals may be used for both calendar dates in modern Japanese and Korean languages, but not for Chinese old-style dates.

Japan started using the Gregorian calendar on 1 January 1873,[24] locally known as "the first day of the first month of Meiji 6" (明治6年1月1日,Meiji rokunen ichigatsu tsuitachi?). The preceding day, 31 December 1872, was "the second day of the twelfth month of Meiji 5" (明治5年12月2日,Meiji gonen jūnigatsu futsuka?).

Japan currently uses two eras: the Western era and a modified traditional Japanese era name (nengō). The months and days are those of the Gregorian calendar, but the year is either the Western year number or a year of the nengō of the emperor on the throne. Since 1873, an era and the first year of that era has begun on the day of the year that the emperor ascended the throne. The second year of that era began on the next 1 January even if the first year contained only a few days. All subsequent years of that era began on 1 January until that emperor died. For example, the first year of the Showa Era, that of Emperor Hirohito, contained only the last six days of 1926, while Showa 64, his last year, contained only the first seven days of 1989. The current Gregorian year 2015 corresponds to Heisei 27.

Korea started using the Gregorian calendar on 1 January 1896, which was the 17th day of the 11th lunar month not only in Korea but also in China, which still used the lunisolar calendar.[25] The lunisolar Korean calendar is now used for very limited unofficial purposes only. The North Korean calendar uses Gregorian months and days, but with Kim Il-Sung's year of birth (1912) used as year 1.

The Republic of China government under Provisional President Sun Yat-sen abolished the lunisolar Chinese calendar and adopted the Gregorian calendar on 1 January 1912. The public, however, resisted the change and continued to observe traditional holidays. President Yuan Shikai switched to a dual-calendar policy, under which the Gregorian calendar was to be used for most purposes except traditional holidays, which were to be timed according to the Chinese calendar. The geographical reference for China standard time (UTC+8) has been longitude 120°E since 1929. When the Communists took over China in the late 1940s they kept this two-calendar system for the People's Republic of China. Today China, Hong Kong, Macau, Malaysia, Indonesia, Singapore and Taiwan all observe traditional holidays based on the traditional calendar, such as Lunar New Year, while timing other holidays, especially national anniversaries, according to the Gregorian calendar.

In China national guidelines (GB/T 15835-1995, General rules for writing numerals in publications) require writing new style dates with Arabic numerals but old-style dates with Chinese characters. The use of Arabic numerals is considered overly casual for old-style dates.

In Taiwan it is common to see Arabic numerals in new-style dates, though Chinese characters sometimes appear in these. Chinese characters are normally used for old-style dates. The calendar year in Taiwan is determined according to traditional custom of era names, but using the founding of the Republic of China government in 1912 as the start rather than the regnal year of an emperor.

In the book Strange Adventures of Captain Dangerous by George Augustus Henry Sala, the narrator says "The year of our Lord is seventeen hundred and eighty. His Majesty's subjects have lost eleven days—through some Roguery in high places, you may be sure—since I was a young man; and were I a cocksloch, I might grudge that snipping off of the best part of a fortnight from an Old Man's life."

In one of the many peculiar digressions in Thomas Pynchon's novel Mason and Dixon, the same missing eleven days are said to be inhabited by a race of phantom pygmies.

^Stockton, J.R. Date Miscellany I: The Old and New Styles "The terms 'Old Style' and 'New Style' are now commonly used for both the 'Start of Year' and 'Leap Year' [(Gregorian calendar)] changes (England & Wales: both in 1752; Scotland: 1600, 1752). I believe that, properly and historically, the 'Styles' really refer only to the 'Start of Year' change (from March 25th to January 1); and that the 'Leap Year' change should be described as the change from Julian to Gregorian."

^ abcSpathaky, Mike Old Style New Style dates and the change to the Gregorian calendar. "increasingly parish registers, in addition to a new year heading after 24th March showing, for example '1733', had another heading at the end of the following December indicating '1733/4'. This showed where the New Style 1734 started even though the Old Style 1733 continued until 24th March. .. We as historians have no excuse for creating ambiguity and must keep to the notation described above in one of its forms. It is no good writing simply 20th January 1745, for a reader is left wondering whether we have used the Old or the New Style reckoning. The date should either be written 20th January 1745 O.S. (if indeed it was Old Style) or as 20th January 1745/6. The hyphen (1745-6) is best avoided as it can be interpreted as indicating a period of time."

^A Julian leap year is every year divisible by 4. A Gregorian leap year is a year exactly divisible by 4 but not by 100 unless it is exactly divisible by 400. So 1600 and 2000 were leap years under both calendars, but the other centuries (e.g. 1700, 1800, 1900) were leap years under the Julian calendar but not the Gregorian calendar. The Gregorian calendar did not exist until 1582. The extension of the Gregorian calendar before 1582 is called the Proleptic Gregorian calendar, in which the years 400, 800, and 1200 are leap years but other century years are not.

^See Cal (Unix)#Features and the Oracle Solaris manual: "An unusual calendar is printed for September 1752. That is the month 11 days were skipped to make up for lack of leap year adjustments".